1. Field of the Invention
Embodiments of the present invention relate generally to the field of optics; more particularly to optical apparatus, methods and applications that provide and utilize the phenomena of extraordinary transmission of light through a sub-wavelength-sized aperture and, most particularly to the extraordinary transmission of light through a dielectric-filled aperture(s) in a real metal film.
2. Technical Background
Ebbesen et al. reported the discovery of extraordinary transmission through sub-wavelength aperture arrays (T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, P. A. Wolff, Nature 391 (1998) 667). Leven et al. developed zero-mode waveguides of diameters ˜ 1/10 of the illumination wavelength in order to measure single molecule chemical reactions in a nanoscopically restrained optical volume (M. J. Levene, J. Korlach, S. W. Turner, M. Foquet, H. G. Craighead, W. W. Webb, Science 299 (2003) 682). The proper operation of these nano-optical devices in recent single molecule spectroscopy experiments is crucially dependent on the confinement of light at the entrance of waveguide. The study of transmission through sub-wavelength apertures is particularly interesting for its potential applications in near-field scanning optical microscopy, high-resolution optical lithography and high-density optical data storage. In addition to aperture arrays, it has also been demonstrated that transmission through an isolated aperture is enhanced if the aperture is surrounded by certain periodic structures at its entrance surface (T. Thio, K. M. Pellerin, R. A. Linke, H. J. Lezec, T. W. Ebbesen, Opt. Lett. 26 (2001) 1972), and beaming of the transmitted light can occur if the exit surface is also textured (H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, T. W. Ebbesen, Science 297 (2002) 820).
Transmission through a single cylindrical aperture and apertures of other shapes (e.g, C-shaped; H-shaped, others) has been investigated extensively in recent years in order to gain understanding of the mechanisms behind enhanced transmission and make use of this phenomenon in applications such as near-field scanning optical microscopy. While enhanced transmission can be achieved in some of the reported scanning probe designs with novel aperture shapes, the large overall probe sizes used in these designs make them undesirable, particularly for imaging delicate samples.
It has also been reported that transmission can be enhanced if a hole is filled with a dielectric material due to the increase of the cutoff wavelength. However, for wavelengths above the cutoff, transmission is still very low because no propagating modes are allowed inside the aperture.
The inventors have recognized the many benefits and advantages realizable by an optical apparatus that can provide enhanced (extraordinary) transmission through a sub-wavelength aperture, which overcomes the shortcomings known in the art for such apparatus and applications.